1. Field of the Invention
The present invention relates to an inductive element for use in various electronic appliances, especially cores for use in inductive elements, and transformers and inductors comprising the core for use in the inductive element.
2. Description of the Related Art
Inductive elements such as transformers for increasing or decreasing electric voltages or for transforming the amount of electric current, or inductors that function as self-inductance have been indispensable to various kinds of electronic appliances.
Demands for compacting and thinning electronic appliances are increasing in recent years, posing problems to make the inductive elements to be integrated into these electronic appliances compact and thin.
Cores for the inductive elements having thinner shapes than conventional EI cores and toroidal cores are proposed as a mean for solving the problems of compacting and thinning the inductive elements described above.
The inductor making use of this core for use in the inductive elements will be described hereinafter referring to the drawings.
As shown in FIG. 20A, the inductor 1 is a type for packaging into a printed board, which is provided with a core 2 for the inductive head, printed board 3 and a lead wire 11.
A base plate 4 and a base core 6, comprising a magnetic substance provided with rectangular parallel-piped projections 5, 5 and so forth projected out of the top face of the base part 4 forming a matrix with three columns and rows aligned by a given distance apart, are provided on the core 2 for the inductive element. The rectangular parallel-piped projections 5, 5 and so forth are formed to have the same height with each other.
Grooves 10 divided by the side faces 13 and 13 of the projections 5 and 5 of two rectangular parallel-piped projections and the base plate 4 are provided on the base core 6 as shown in FIG. 20A. In the configuration shown in FIG. 20, the numbers of the Grooves 10 accounts for 12 since there are nine projections 5, 5 and so forth.
A cover core 7 comprising a plate of magnetic substance is provided on the core 2 for the inductive element.
The printed board 3 is composed of an insulation plate 3a such as a glass-epoxy plate, holes 12, 12 and so forth for allowing the rectangular parallel-piped projections 5, 5 and so forth on the base core 6 to penetrate are drilled through the insulation plate 3a.
A lead wire 11 and the printed board 3 are disposed so as to be sandwiched between the base core 6 and cover core 7.
In more detail, the lead wire 11 comprising a wire material of a metal is mounted on the base core 6 so as to crawl through all the twelve grooves 10, 10 and so forth. Both ends 11a and 11 a of the lead wire 11 is joined to the other electronic circuits.
Then, The printed board 3 is mounted on the top face of the base core 6 so that the rectangular parallel-piped projections 5, 5 and so forth are allowed to penetrate through the holes 12, 12 and so forth.
Finally, the cover core 7 is mounted on the printed board 3 by adhering the top faces 8, 8 and so forth of the rectangular parallel-piped projections 5, 5 and so forth penetrating through the printed board 3 with the bottom face 9 of the cover core 7.
As shown in FIG. 20B, mutually independent closed magnetic circuit for allowing a magnetic flux generated by the voltage impressed on the conductor 11 is formed in the inductor 1 described above with the rectangular parallel-piped projections 5 and 5, the base plate 4 and the cover core 7. These closed magnetic circuits are referred to unit core 15, 15 and so forth (the inside surrounded by dotted lines). The numbers of the unit cores 15 are twelve since twelve grooves 10 are provided.
Therefore, the core 2 for the inductive element assumes a construction in which a plurality of unit cores 15 are disposed on the same plane.
The lead wire 11 serves as an inductive element that induces inductance, which is determined by the cross sectional area of the magnetic circuit of the unit core 15 and magnetic permeability of the magnetic substance, when it passes through the unit core 15. When the lead wire 11 passes through a plurality of the unit cores 15, 15 and so forth, the inductance value obtained is proportionally increased.
Accordingly, the lead wire 11 may be allowed to pass through a lot of unit cores 15, 15 and so forth when a large inductance value is necessary.
When two strings of lead wires 11 pass through the grooves 10, 10 and so forth of the core 2 for the inductive elements, it is also possible to form a transformer in which one string of the lead wire 11 serves as a primary coil and the other string of the lead wire serves as a secondary coil.
According to the core 2 for the inductive element, the dimension of the core can be made thin since the unit cores 15 are disposed on one face of the base core 6.
The numbers of the unit cores 15 can be readily increased or decreased by increasing or decreasing the numbers of the rectangular parallel-piped projections 5, 5 and so forth.
Furthermore, the core for the inductive head may be used for a transformer by adjusting the number of the lead wires.
The dimension of the inductor 1 as hitherto described can be made thin since it is provided with the core 2 for the inductive element.
A prescribed level of inductance can be induced in the inductor 1 described above with one or more of the unit cores 15 provided on the core 2 for the inductive element and the lead wire 11 passing through these core units 15.
By adjusting the numbers of the unit cores 15 through which the lead wire 11 passes, or by allowing the lead wire 11 to pass through a part of the core units 15, the inductance level of the foregoing inductor 1 can be readily adjusted.
Ferrite materials such as a Mn--Zn ferrite and a Ni--Zn ferrite or metallic materials such as permalloy, sendust and metallic materials such as an amorphous metal alloy have been used for the materials of the core 2 for the inductive element.
However, there remained a problem in the inductor 1 produced by using conventional ferrite materials that core loss of the core 2 of the inductive element becomes large when an alternate current in a high frequency band is impressed.